A joint is formed when two or more bones meet and are joined by elastic, fibrous or cartilaginous tissue, or a combination of the three. Joints are also called articulations (as in lorries). There are about 230 joints in human body. Study of joints explains how the bones are interconnected in the body. All body movements involve bending of different bones at various joints. Body activities like breathing, talking, sitting, standing, walking, performing physical work either in office, fields, kitchen or household, games & sports involves extensive use of various joints. Typical joints or articulation means where two or more bones are interconnected.
Based on type of movements joints are classified as
Synarthrosis or immovable joints: In this type two bones are held together with the help of cartilage or fibrous tissue and they show no movements. Examples are joints of skull bones, teeth and jaw.
Amphiarthrosis or slightly movable joints: In this type bones are connected through cartilage or fibrous tissue and shows very little or restricted movement. Examples are sacro-iliac joint, tibia-fibula joint.
Diarthrosis or freely movable joints or synovial joints: In this type the bones are held together through synovial membranes and shows free movements. Based on plane of movements they may further categorized as:
Monoaxial: showing single plane of movement e.g. elbow joint.
Biaxial: showing two planes of movements e.g. wrist and ribs
Triaxial: showing movements in all three planes e.g. hip and shoulder.